®
RT6255A/B
5A, 18V, 500kHz, ACOT
TM
Step-Down Converter
General Description
The RT6255A/B is a high-performance, synchronous step-
down DC-DC converter that can deliver up to 5A output
current from a 4.5V to 18V input supply. The device
integrates low R
DS(ON)
power MOSFETs, accurate 0.6V
reference and an integrated diode of bootstrap circuit to
offer a very compact solution.
The RT6255A/B adopts Advanced Constant On-Time
(ACOT
TM
) control architecture that provides ultrafast
transient response and further reduces the external-
component count. In steady states, the ACOT
TM
operates
in nearly constant switching frequency over line, load and
output voltage ranges and makes the EMI filter design
easier.
The device offers Independent enable control input pin and
power good indicator (TSOT23-8 only) for easily sequence
control. To control the inrush current during the startup,
the device provides a fixed 1.5ms soft-start up. Fully
protection features are also integrated in the device
including the cycle-by-cycle current limit control, UVP,
input UVLO and OTP.
The RT6255A/B is available in the TSOT-23-6 (FC) and
TSOT-23-8 (FC) package.
Features
Input Supply Voltage Range : 4.5V to 18V
Output Current : 5A
Advanced Constant On-Time (ACOT
TM
) Control for
Ultrafast Transient Response
Steady Switching Frequency : 500kHz
�½
Forced PWM Mode (RT6255B)
�½
Pulse-Skipping Mode (PSM) at Light Load
(RT6255A)
Optimized for Low-ESR Ceramic Output Capacitors
Programmable Output Voltage : 0.6V to 5V
Ω
Ω
Internal 45mΩ Switch and 23mΩ Synchronous
Rectifier
Cycle-by-Cycle Current Limit Protection
Internal Soft-Start (Typ 1.5ms) or Externally
Adjustable, Pre-biased Compatible Soft-Start (Only
for Option with SS Pin)
Power Good Indicator (90%) (Only for Option with
PGOOD Pin)
Output Under-Voltage Protection (UVP)
Over-Temperature Protection (OTP)
Input Under-Voltage Lockout (UVLO)
Available in TSOT-23-6 (FC) and TSOT-23-8 (FC)
Packages
Applications
Set Top Box
Portable TV
Access Point Router
DSL Modem
LCD TV
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6255A/B-03 October 2018
www.richtek.com
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RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
